1. Field of the Invention
This invention relates generally to an oscillator for a synchronous detection using a phase-locked loop, and more particular to an oscillating circuit which can produce a first reference signal for a phase-locked loop and a second reference signal having a 90.degree. phase difference with respect to the first reference signal effecting synchronous detection.
2. Description of the Prior Art
It is known in the art to use a phase-locked loop circuit for producing a reference carrier for synchronous detection. However, in a conventional phase-locked loop circuit, a phase of an output reference signal is different by 90.degree. from that of an input signal. As a result an additional phase shifter is needed to make the phase of the reference coincide with the phase of input signal to be detected.